Turn Angle φ as a Function of Determinism Ratio Ψ. The determinism ratio Ψ is a dimensionless number calculated from θc, δ, and τ. The turn angle φ is plotted as a function of Ψ. hree states emerge when the turn angle φ is plotted as a function of the determinism ratio Ψ. At φ = -180° random migration dominates. The growth cone always collapses. The second state is a transition region where deterministic and stochastic motions are balanced. This region occurs over a narrow region where random migration and deterministic migration are comparable. At φ = 0° deterministic migration dominates. Growth cone migration is unaffected by size or placement of the constraint region.